GitLab

Use new method ServiceConnection::FlushForTesting instead of
RunUntilIdle.

Change-Id: I032a428465ac661905ac3cfe466a898c4ca015bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2398722Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Oleh Lamzin <lamzin@google.com>
Cr-Commit-Position: refs/heads/master@{#805655}